The present invention relates to a water-based fluorine-containing paint which is curable at ambient temperature.
Fluororesins are generally excellent in chemical resistance, weather resistance and heat resistance, and in view of these favorable properties the use of fluororesin based paints is increasing in various fields.
As a fluororesin suitable for solvent-thinned paints, U.S. Pat. No. 4,631,326 discloses a fluorine-containing copolymer comprising chlorotrifluoroethylene, a vinyl or isopropenyl ester of fatty acid and a hydroxyl-containing allyl ether, This allyl ether provides a functional group to the copolymer for curing the copolymer. Japanese Patent Unexamined Publication No. 57-34107 discloses a fluorine-containing copolymer which is curable at ambient temperature and comprises a fluoroolefin, cyclohexylvinyl ether, an alkylvinyl ether, and an hydroxyalkylvinyl ether. This hydroxylalkylvinyl ether provides a functional group to the copolymer for curing the copolymer.
Fluororesin-containing solvent-thinned paints are widely used as weather resistant paints in the fields of architecture, automobile and chemical engineering. Furthermore, in view of the environmental protection, fluororesin-containing water-based paints, powder paints, and high-solid paints have been developed, too. Each fluororesin for these paints comprises a fluorocarbon as a rain component, such as chlorotrifluoroethylene, tetrafluoroethylene or vinylidene fluoride, and a copolymerizing hydrocarbon monomer such as vinyl ester or vinyl ether, which is added for the purpose of increasing solubility of the fluororesin. It has been difficult to provide the above-mentioned fluororesin-containing water-based paint with a functional group for forming a cross-linking structure, Therefore, a so-called lacquer-type water-based paint in the form of emulsion of a high-molecular compound prepared by emulsion polymerization was used in many cases of the coating step. In view of this, a hardener for forming a cross-linking structure at ambient temperature was developed, such as an oxazoline compound or a self-emulsifiable polyisocyanate. The hardening action by the polyisocyanate, however, tends to terminate due to the reaction of isocyanate group with water (dispersion medium). Thus, it has been necessary to add the polyisocyanate to vehicle, immediately before the coating step, in view of pot life of the paint. However, a conventional self-emulsifiable polyisocyanate is insufficient in dispersibility in water. Thus, it has been difficult, particularly in a coating site, to uniformly finely disperse the polyisocyanate in water. With this, a coated film becomes insufficient in water resistance, weather resistance, stain resistance and the like.
In contrast to the above-mentioned two-package type paints, there have been proposed one-package type paints in the field of water-based acrylic-ester paints. For example, Japanese Patent Unexamined Publication No. 57-3850 discloses a water-based disperse system containing, as a disperse phase, carbonyl-containing copolymer particles. Japanese Patent unexamined Publication No. 4-81447 discloses a water-based emulsion composition which is a mixture of a self-emulsifiable polyurethane and a water-based acrylic-resin emulsion which is cross-linkable at ambient temperature.
Similar to the above-mentioned acrylic ester paint, there has been a recent demand for a water-based fluorine-containing paint which is one-package type and capable of providing a coated film superior in water resistance, weather resistance, stain resistance and the like.